1. Field of the Invention
The present invention relates to a method of ultrasonic imaging and an ultrasonic imaging apparatus for using ultrasonic waves in order to perform diagnosis of internal organs of living bodies or a non-destructive inspection.
2. Description of a Related Art
In general, an ultrasonic imaging apparatus including an ultrasonic diagnostic apparatus and industrial flaw detector uses an ultrasonic probe including a plurality of ultrasonic transducers with the functions of transmitting and receiving ultrasonic waves. The ultrasonic imaging apparatus with an ultrasonic probe uses a scanning line formed by combining ultrasonic waves to scan the objects in order to provide image data about an object to be inspected. In such an apparatus, two-dimensional or three-dimensional images of the object can be reproduced on the basis of the image data.
In such an ultrasonic imaging apparatus, as for the method of transmitting and receiving ultrasonic beams using an ultrasonic probe, the following two methods described in (1) and (2) have been known. In addition, the design of ultrasonic beam is described in xe2x80x9cDigital Ultrasonic Technologyxe2x80x9d by H. Kanda et al., a special issue of the Japanese Journal of Clinical Radiology, Vol. 43, No. 11, pp. 1248-1252, published in 1998.
(1) Unidirectional ultrasonic beam transmissionxe2x80x94Echo division receiving method
FIG. 6A is a schematic diagram illustrating an example of ultrasonic beam transmitting states according to a conventional method. Likewise, FIG. 6B is a schematic diagram illustrating an example of ultrasonic beam receiving states.
In this method, each of plural ultrasonic transducers 102 included in an ultrasonic probe 100 transmits ultrasonic pulses intermittently in accordance with drive signals supplied by a plurality of pulsers connected to a transmitting section. This ultrasonic pulse is transmitted from the ultrasonic probe 100 to the object to propagate through the object and form an ultrasonic beam 101, as shown in FIG. 6A. The ultrasonic beam 101 becomes narrower as it travels in the transmission source nearby area and narrowest at the focal point F, and thereafter diverges progressively. The ultrasonic beam is reflected by a reflector in the object to generate an echo. The ultrasonic probe 100, as shown in FIG. 6B, receives this echo. The detection signals output from the plural ultrasonic transducers 102 included in the ultrasonic probe 100 undergo a predetermined delay through a plurality of phase matching calculating units connected to a receiving section and they are added to each other to provide a detection signal for each received ultrasonic beam. In this example, three received ultrasonic beams 103, 104, and 105 are illustrated.
(2) Multi-directional ultrasonic beam transmissionxe2x80x94Echo undivision receiving method.
FIG. 7 is a schematic diagram illustrating another example of ultrasonic beam transmitting and receiving states according to a conventional method.
In this method, an ultrasonic probe 100 is supplied with two or more kinds of drive signals, whereby a plurality of ultrasonic transducers 102 included in the ultrasonic probe 100 are simultaneously supplied with more than one kind of drive signals by pulser sets. For example, as shown in FIG. 7, two sets of timing pulses composed of A-series pulses and B-series pulses are applied to one set of elements to generate both of an ultrasonic beam A and ultrasonic beam B. When the A-series pulses and the B-series pulses overlap one another, a common pulse is produced. These ultrasonic beams A and B are transmitted toward the object simultaneously in a plurality of directions, e.g. two directions.
For above-described ultrasonic diagnostic method and ultrasonic diagnostic apparatus, it has been required to improve a frame rate and resolution in recent years.
The invention was made in consideration of the foregoing. The first object of the invention is to provide an ultrasonic imaging method and an ultrasonic imaging apparatus which can obtain image data with a high frame rate. Further, the second object of the invention is to improve resolution in the ultrasonic imaging method and an ultrasonic imaging apparatus as mentioned above.
To solve the challenges above described, an ultrasonic imaging method according to the invention, of scanning a measurement target in an object to be inspected by using ultrasonic beams and receiving echoes of the ultrasonic beams reflected by the measurement target to obtain image data on the measurement target, comprises the steps of: (a) transmitting ultrasonic beams simultaneously in a plurality of directions toward the measurement target; and (b) processing detection signals obtained by detecting the echoes so as to form a plurality of receiving focal points with respect to each of the transmitted ultrasonic beams.
In addition, an ultrasonic imaging apparatus according to the invention, for scanning a measurement target in an object to be inspected by using ultrasonic beams and receiving echoes of the ultrasonic beams reflected by the measurement target to obtain image data on the measurement target, comprises: transmission side signal processing means for providing drive signals; an ultrasonic probe for transmitting ultrasonic beams by using a plurality of ultrasonic transducer elements in accordance with the drive signals provided by the transmission side signal processing means and detecting echoes of the transmitted ultrasonic beams to obtain detection signals; reception side signal processing means for amplifying the detection signals output from the ultrasonic probe and obtaining image data on the measurement target on the basis of the amplified detection signals; and control means for controlling the transmission side signal processing means to transmit ultrasonic beams simultaneously in a plurality of directions toward the measurement target from the plurality of ultrasonic transducer elements and controlling the reception side signal processing means to process the detection signals obtained by ultrasonic probe and form a plurality of receiving focal points with respect to each of the transmitted ultrasonic beams.
According to the invention, it is possible to increase the number of ultrasonic beam transmit/receive operations to be performed per unit time and to perform ultrasonic imaging at a high frame rate.